Michael R. Bloomberg has instructed advisers to draw up plans for a potential independent campaign in this year’s presidential race. His advisers and associates said he was galled by Donald J. Trump’s dominance of the Republican field, and troubled by Hillary Clinton’s stumbles and the rise of Senator Bernie Sanders of Vermont on the Democratic side.

Mr. Bloomberg, the billionaire former mayor of New York City, has in the past contemplated running for the White House on a third-party ticket, but always concluded he could not win. A confluence of unlikely events in the 2016 election, however, has given new impetus to his presidential aspirations.

Mr. Bloomberg, 73, has already taken concrete steps toward a possible campaign, and has indicated to friends and allies that he would be willing to spend at least $1 billion of his fortune on it, according to people briefed on his deliberations who spoke on the condition of anonymity because they were not authorized to discuss his plans. He has set a deadline for making a final decision in early March

Bloomberg’s “lead by example” platform would include pledging to do away with armed presidential security to prove to everybody that guns don’t make us any safer, right?